Some of these gripes apply to Faction henchies to, but for the moment I'm really annoyed at the Prophecies henchies.
1) Underpowered henchies. In Maguuma Jungle, just an example, the henchies are level 15. The centaurs are level 16. The Jungle Skales are level 19. The wind Riders are level 17. The Jungle Trolls are level 18. These henchies are also equipped with crappy armor, too (AL 40-45 for casters). They die fast and often.
2) Grouping AI. The henchies have a very bad habit of clustering around the player, making AoE affects (like Cry of Frustration) very powerful against them. This applies to Factions as well.
3) No interrupts. Every mesmer and ranger should have at least one interrupt. Warriors have plenty of interrupts available to them as well. Every time I see a mob execute Troll Unguent or Meteor shower I groan.
4) Poor setups. Alesia [Healer Henchman] uses Orison of Healing, Healing Touch, Heal Other, and Restore Life. At least, at lower levels. Besides being suicidal in her ressurecting, her healing is very slow and inefficient. None of the more useful support heals are used, like Vigorous spirit. Considering she stands still when most monks would try and dodge, she could use a much needed boost, like perhaps using essence bond on herself so she'd get more energy from being whacked on so much so at the least standing still isn't quite so detrimental.
5) Poor setups. There is no real mesmer henchman. I've found I'm more useful with henchmen as a mesmer (even if it's my secondary) than as any other class, including monk. That's because henchies bring no interrupts or other useful domination spells. Empathy is not that great. Cry of frustration, guilt, diversion, and other skills contribute much more to the battle. I cannot say I've found Factions mesmer henchies very useful, either.
6) Poor setups. Everyone else doesn't do nearly enough damage. Thom doesn't bring a self heal. Orion loves to spam fire storm, which sends the fighter henchies chasing after and often aggroing more mobs.
7) Everything else that's been mentioned a hundred times over, mostly which is AI related.
Please continue to support Prophecies and fix the henchmen. I can only imagine 2 years from now everyone seeing Tyrian Grandmaster Cartographer title and seeing it as a badge of putting up with all of the troubles of Tyria, like the poor henchies, very large <lvl 20 land area, ect...